XML 57 R47.htm IDEA: XBRL DOCUMENT
v3.20.4

Revenue from Contracts with Customers - Additional Information (Details) | 3 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019
Revenue from Contract with Customer [Abstract] |  |
Revenue streams percentage, contract with customer | 5.40% | 4.40%

X
- References No definition available. + Details
Name: | us-gaap_RevenueFromContractWithCustomerAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Revenue From Contract With Customer, Percentage + References No definition available. + Details
Name: | wfsl_RevenueFromContractWithCustomerPercentage
Namespace Prefix: | wfsl_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration